It is known that 5HT.sub.3 antagonists exhibit an antiemetic activity, an antianxious activity, a suppressing activity of mental disorders, etc. [Trends in Pharmacological Sciences, 8, 501 (1987)]. 5HT.sub.3 antagonists are effective against carcinostatic agent-induced vomiting, which has not been cured by dopamine antagonists. The 5HT.sub.3 antagonists are thus expected to be antiemetics of new type [Br. J. Cancer, 56, 159 (1987)].
It is disclosed in Japanese Published Unexamined Patent Application No. 72886/85 (U.S. Pat. No. 4,797,406) that quinoline derivatives represented by formula (A): ##STR2## wherein R.sup.4 represents hydrogen, hydroxy or a lower alkoxy (C.sub.1 to C.sub.4); X.sup.1 represents --O-- or --NH--; and p represents 0 or 1, have a 5HT.sub.3 antagonizing activity and an antiarrhythmic activity. That publication merely discloses a compound having azabicyclononane ring (p=1) in formula (A) (hereafter referred to as Compound C): ##STR3## but is silent about any specific compounds having azabicyclooctane ring (p=0). It is also disclosed in Japanese Published Unexamined Patent Application No. 41429/88 (GB-A-2193633) that the compounds represented by formula (A) are effective against vomiting caused by carcinostatic agents such as Cisplatin. Further, Japanese Published Unexamined Patent Application No. 203365/89 (EP-B-0323077) describes quinoline derivatives represented by formula (B): ##STR4## wherein X.sup.2 represents a single bond or CO, and R.sup.4, X.sup.1 and p have the same meanings as described above, but no specific compounds having formula (B) are disclosed therein.